4. Case Studies of Forest Decline Caused by Air Pollution
4.2. The effect of industrial pollution of forest ecosystems
of Russia. More than 10 million people live in the North. Cities and towns are isolated. Energy is provided by burning coal, liquid fuel, and wood at big and small power stations and in the homes. As a result, significant amounts of pollutants are emitted to the atmosphere, mostly SO2 and dust. The areas of polluted territories around such towns exceed markedly the territories of the towns themselves (Zony Zagryazneniya…, 1988). The transport pressure on fragile northern soils creates additional stresses. As a result the territories around northern towns are eroded and the vegetation cover is severely damaged. A high demand on fuel wood leads to deforestation, which is especially intensive in the northern regions due to the low growing stock (6–20 m3 per hectare). The total area of anthropogenic tundra, created as a result of deforestation, is about 470,000–500,000 km2 in the whole Subarctic zone.
The largest area of forest decline due to emissions is situated in Siberian Subarctics, in the south-western part of Taimyr peninsula around Norilsk polymetallic industrial complex (Krasnoyarsk kray), including, in fact, 5 industrial cities. The main component of emissions Table 4.2. Allowable air concentration units of pollutants. (After Kryuchkov (1993), for trees;
and Mnatsakanyan (1992), for cities).
Allowable single concentrations, mg/m3:
Average daily
concentrations, mg/m3:
Compounds For trees For cities For trees For cities
Nitrogen dioxide 0.04 0.085 0.02 0.04
Sulphur dioxide 0.3 0.5 0.015 0.05
Vapours of sulphuric acid 0.1 0.3 0.03 0.1
Chlorine 0.025 0.1 0.015 0.03
Fluoric acid (HF) 0.004 0.02 0.0005 0.005
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(96–98% by weight) is sulphur dioxide. The rest includes nitrogen oxides, CO, chlorides, phenol and other substances. Dust emissions contain copper, nickel, cobalt. According to Natsionalnyi doklad (1991), annual emission of sulphur compounds to the atmosphere exceeds 2.2 million tons. In 1993, the emission exceeded 2.7 million tons. The water of the region is also severely polluted. Average annual concentrations exceeded allowable levels by the factor of 115 for copper, by the factor of 30 for nickel, by the factor of 8 for ammonium and by the factor of 4 for organic substances. These conditions have led to serious losses of fish. The enterprises of Norilsk produce annually 1,100 tons of toxic solid wastes, 5 million tons of slag, 12 million tons of ground deposits, which occupy up to 2,000 ha. Based on all these factors, the region of Norilsk is considered to have the most critical ecological conditions.
A seven-fold increase of the area of declining forest was observed during the last decade in Norilsk. The total area of dead forests around Norilsk was 310,000 ha by 1992 (Martynyuk and Kasimov, 1993). According to another estimate, the area with dead forests was 382,000 ha (Natsionalnyi Doklad, 1991). Damaged forests were observed at a distance of 200 km to the south from Norilsk. At a distance of 35 km, spruce and larch trees contained 5–10 times more copper than trees outside the affected area. Structural and functional organization of plant communities is altered. At a distance of 120 km, the natural regeneration of trees is absent, annual increment and primary biological production are very low.
The extent of forest die-back varies from year to year (Table 4.3). One reason for this variation might be the inventory process itself, as the collection of data about the effect of atmospheric pollution is irregular and fragmentary (Obzor Sanitarnogo Sostiyaniya, 1994).
Kryuchkov (1991) made a detailed investigation of the consequences of the northern forest pollution. In fact, it was conducted not in Norilsk, but in quite similar conditions, and the results might also be applied to the description of Norilsk forests. The information about Norilsk itself was not available for publication.
Northern ecosystems are quite specific and forest decline leads to some specific consequences.
At deforested territories the climatic conditions became more severe than in typical arctic ecosystems. There is an increase of wind rates, snow density, depth of frozen soil. Changes in air and soil temperatures are observed. After the death of mosses, lichens and undershrubs the upper organic soil horizon is destroyed.
According to Kryuchkov (1991), several bioindicators were chosen and ranged by their sensitivity to describe the extent of subarctic forest degradation (see also Table 4.4).
Table 4.3. The dynamics of forest die-back around Norilsk (Krasnoyarsk kray).
31 1. Presence and absence of lichens and mosses.
2. The state of coniferous trees - age, color, necroses of needles.
3. Undershrubs: their diversity and coverage.
4. Completeness and thickness of soil profile.
Five zones of degradation were then identified.
Zone I.
Zone of complete ecosystem degradation. The plants are dead, soil organic horizons are destroyed, mineral soil horizons are exposed to the surface. The whole soil profile is often eroded, and soil cover is represented by parent material. Some fragments of soil and vegetation cover can be found in ravines. Trees are represented by suppressed birch and willow. Single spruce trees can be found, their needles being 1–2-years old (compared to 14–16 years under normal conditions). Local climatic conditions are altered – wind rates increased and the temperature becomes 1–3 centigrades lower. No moss or lichen cover is found at the surface of big stones.
Zone II.
Zone of strong ecosystem degradation. Soil organic horizons are destroyed, “color spot tundra” is formed. Coniferous trees (spruce) are dead, single individuals are alive but dying.
Suppressed birch bushes are found at flat and elevated sites. The trees are isolated and cannot form a phytocoenosis. Dwarf forms of spruce and birch with suppression features are common.
Lichens are absent. Moss bogs are replaced either by dry valleys or by Carex associations.
Unfavorable meteorological conditions are very dangerous for the trees in this zone, for example, when there is no wind, no pollutant removal occurs, and pollutant-containing cloud expands and effects more and more trees. Sharp increase of technogenically deforested territories occurs, especially after emergency discharge. After the death of needles or leaves, the temperature and water exchange of a tree is altered, leading to further decline.
Around Norilsk, the territories that could be referred to the zones I and II, occupy the area of 300,000 ha (Natsionalnyi Doklad, 1991).
Table 4.4. Plant resistance to air pollution – critical concentrations for different groups of plants, mg/m3 (after Kryuchkov, 1991).
Plants SO2 Ni oxide Cu oxide Dust HF
Epiphytic fruticose lichens < 0.003 < 0.001 < 0.002 0.01 0.001 Epiphytic foliose lichens, Sphagnum mosses 0.003
-0.007 Larch, ground cedar (Juniperus) 0.009
-0.05*
0.001* 0.002* 0.03 -0.05*
0.004 -0.005*
Deciduous trees and bushes – birch (Betula sp.) and rowan-tree (Sorbus sp.)
0.05 Bushy forms of willow, aspen, alder;
berries - undershrubs;herbs
* - Second marked values are equal to sanitary normatives.
32 Zone III.
Zone of markedly destroyed northern taiga ecosystems. Its area is about 380,000 ha around Norilsk complex (Natsionalnyi Doklad, 1991). Within this zone, the northern taiga forests are transformed into suppressed arctic spruce-birch rarefied forests. Dead spruce forms 30–40% of a stand. Living trees have dry or deformed crowns. The age of needles varies from 2–3 to 6–7 years depending on tree form and degradation stage. Some 30–50% of birch trees have dried crowns. The projective cover of mosses and grasses increases from 20–30% to 60–80%. Small fragments of sphagnum mosses can be found. The retention of pollutant-containing precipitation occurs at crown surface, leading to element concentration and intensified pollution.
Zone IV.
Zone of initial degradation of taiga ecosystems. The main features of disturbance here are drying and deformation of crowns, defoliation, reduction of needle lifetime, leaf and needle necroses, reduced increment, the absence of epiphytous lichens, the suppression of lichens and mosses, and soil cover formations.
Zone V.
Zone of initial degradation. This zone is not subject to constant pollution, however, after emergency discharge and with the absence of winds, pollutant concentration exceed sanitary and especially ecological limits. The age of needles varies between 9 and 13 years. The epiphytic lichens can be found fragmentarily. Zones of initial degradation may occupy large areas.
The destruction of mountainous ecosystems occurs faster compared to plain ecosystems. The technogenic press can be the same, however, climatic conditions are more extreme.
After long-term investigations the following division of vegetation was made for resistance to air pollutants (Table 4.4).
Coniferous forests in the taiga zone can survive for a long time at SO2 concentration in the air being at the level 0.005–0.009 mg/m3. After a long-term influence of SO2 at the content 0.009–
0.05 mg/m3, the degradation of epiphytic lichens is observed after 10–15 years, and after 30–
50 years the decline of coniferous forests occurs. There is no complete regeneration of forests under such conditions. Taking into account that there is an accumulation effect by other pollutants, the tree lifetime might decrease. At SO2 concentrations between 0.05 and 0.07 mg/m3 coniferous trees die after 10–20 years. Only larch and some deciduous species can exist under such conditions.
The input of organic matter and mineral fertilizers can increase forest lifetime. But the most important measure is the reduction of emissions. In 1991, a special program was adopted, including the introduction of new purification technologies. The following reduction of SO2
emissions was planned, based on the level of 1990: 19% by 1995, 40% by 2000 and 73% by 2005 (Natsionalnyi Doklad, 1991). Moreover, water uptake for industrial needs and the discharge of liquid wastes should be seriously reduced. However, for a moment, there is no information available about the implementation progress of this program.
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5. Conclusion
Siberian forests are subject to the influence of the whole range of factors leading to forest decline and, in critical cases, to forest die-back. The factors are both natural and anthropogenic. By their significance, natural factors might be ranked as the following: forest fires, unfavorable weather conditions, insect invasions, and diseases. Negative human activities can be ranked as: changes in hydrological regimes, mechanical devastation, soil and air pollution.
In some Siberian regions, natural factors of forest death undoubtedly prevail. At the same time, in many regions the scale of natural and human causes of forest decline are at least comparable (south of the Far East, south of the West Siberia, Krasnoyarsk kray). For some regions the quality of the available information does not allow us to make any comparisons.
The industrial pollution conditions in Siberia are quite different from that described in numerous studies for Europe. In Europe there is a problem at both the national and international scale, and transboundary pollution plays an important role in creating the pollution loads. In Siberia environmental pollution is still a problem at the regional scale. Most parts of territories, damaged by pollution, are concentrated around several huge industrial complexes. In some cases pollution is created around united neighboring pollutant sources, as it happens in Kemerovo oblast or within the industrial region around Krasnoyarsk. At the same time, vast territories are free from pollution influence – Yakutiya, central part of Krasnoyarsk kray, and Magadan oblast. Long-distance pollution transportation does not make any serious contribution to the pollution background in Siberia, with one exception – Tyumen oblast, which is polluted by discharge products from the Southern Urals. In general, it means that severe ecological problems might be solved by ameliorating the “pollution climate” in several specific critical regions.
However, the available information is insufficient to make any definite conclusions and policy recommendations, despite the presence of annual reports, including a review of ecological and sanitary status of Siberian forests. The data represented in the reports are doubtful, especially those concerning pollution causing forest decline. Large forest territories are outside the monitoring of fires or insects. Concerning environmental pollution, only the first attempts have been made to estimate the situation in the Asian part of Russia. The analyses of the pollution conditions in Siberia demonstrated that the damage, caused to forests by air pollution probably should concern larger areas than estimated in the official reports. Case studies, mentioned in the paper, are only first steps in the estimation of real damage of air pollutants to forest ecosystems. Further large investigations are needed to obtain a reliable description of the ecological status of the Siberian forests.
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